(a) Field of the Invention
The present invention relates to a frictional variable transmission for a vehicle.
(b) Description of the Related Art
A transmission functions to deliver engine drive power to the drive wheels. Two basic types of transmissions are the manual transmission, in which the driver manipulates a shift lever to control shifting into different speeds and ranges, and the automatic transmission, in which shifting into the different forward speeds is automatically controlled according to various driving conditions. Another type of transmission is the gearless transmission, which automatically and continuously performs shifting over a single, large range of speeds when in drive and reverse.
FIG. 1 shows a sectional view of a pulley portion of a conventional gearless transmission.
A drive pulley 20 and a driven pulley 30, which are connected by a belt 10, are mounted respectively on a drive shaft 12 and a driven shaft 14. Shifting is realized typically by varying relative functional diameters of the pulleys 20 and 30. The drive pulley 20 includes a first fixed pulley 22 fixedly mounted on the drive shaft 12, and a first variable pulley 24 mounted on the drive shaft 12 and which undergoes rectilinear motion thereon such that the functional diameter of the drive pulley 20 is varied.
The basic structure of the driven pulley 30 is identical to the structure of the drive pulley 20. That is, the driven pulley 30 includes a second fixed pulley 32 and a second variable pulley 34, which operate similarly to the first fixed pulley 22 and the first variable pulley 24.
A shift range of the gearless transmission structured as in the above is determined by the scope of movement of the first variable pulley 24 of the drive pulley 20 and the second variable pulley of the driven pulley 30. A rotational force of an engine passes through a torque converter and the drive shaft 12, and is transmitted to a differential via a power transmission axle that is arranged in parallel with the driven shaft and according to a variations in functional diameter of the drive pulley 20 and the driven pulley 30.
However, the conventional gearless transmission described above has several drawbacks. These include a large number of parts, complicated structure, and significant weight.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a frictional variable transmission for a vehicle that is simple in structure and lightweight.
To achieve the above object, the present invention provides a frictional variable transmission comprising a rotating unit rotated by an engine of the vehicle; a power-varying unit that varies, in a state of contacting the rotating unit, a rotational force transmitted from the rotating unit by moving in a predetermined direction; a hydraulic clutch mounted off-center from the rotating unit, and varying between states of frictional contact with or separation from the power-varying unit by hydraulic pressure generated according to a depressed state of a clutch pedal, thereby controlling transmission of rotational force of the power-varying unit; and a power transmitter linked to the movement of the hydraulic clutch, and transmitting a rotational force corresponding to an input state of rotational force transmitted through the rotating unit and the power-varying unit.
According to a feature of the present invention, the friction generated by the contact of the power-varying unit with the rotating unit and the hydraulic clutch undergoes rolling contact in an elastohydrodynamic region, and an elastohydrodynamic fluid film is formed.
According to another feature of the present invention, if the power-varying unit is positioned at an outer circumference region of the rotating unit, the rotating unit rotates the power-varying unit at a high speed such that the power-varying unit rotates the hydraulic clutch faster than the rotating unit.
According to yet another feature of the present invention, if the power-varying unit is positioned at an inner circumference region of the rotating unit, the rotating unit rotates the power-varying unit at a low speed such that the power-varying unit rotates the hydraulic clutch slower than the rotating unit.
According to still yet another feature of the present invention, if the power-varying unit is positioned on one side of an imaginary center-line of the rotating unit, the rotating unit rotates the power-varying unit in a reverse direction such that the hydraulic clutch is rotated in a direction opposite that of the rotating unit.
According to still yet another feature of the present invention, a crankshaft, which rotates according to operation of the engine, interconnects the rotating unit and the engine, and a frictional face of the rotating unit that contacts the power-varying unit is evenly formed and acts as a frictional flywheel.
According to still yet another feature of the present invention, the crankshaft and the rotating unit are integrally formed.
According to still yet another feature of the present invention, the power-varying unit comprises a shift lever; a shift fork indexed with the shift lever; a shift rod positioned from a circumferential outer direction of the rotating unit to a circumferential inner direction of the rotating unit between the rotating unit and the hydraulic clutch, both ends of the shift rod being fixed; and a shift ball mounted on the shift rod, and which, in a state of being connected to the shift fork, receives rotational force of the rotating unit according to movement from the circumferential outer direction to the circumferential inner direction of the rotation power unit, thereby rotating in a predetermined direction.
According to still yet another feature of the present invention, the shift ball comprises a hole through which the shift rod passes for mounting of the shift ball on the shift rod; a fork-receiving portion linked to the movement of the shift lever and to which the shift fork is connected to enable movement in the axial direction of the shift rod; and a rolling frictional surface formed roughly hemispherically under the fork-receiving portion.
According to still yet another feature of the present invention, the hydraulic clutch comprises a clutch housing; a hydraulic pressure chamber formed in the clutch housing and which generates a predetermined hydraulic pressure according to a depressed state of the clutch pedal; and a friction plate mounted off-center from the rotating unit and connected to a clutch shaft, the clutch shaft moving in a direction of its longitudinal axis according to the generation of hydraulic pressure in the hydraulic pressure chamber such that the friction plate comes into contact with and is separated from the power-varying unit.
According to still yet another feature of the present invention, the clutch shaft and the friction plate are integrally formed.
According to still yet another feature of the present invention, if the clutch pedal is depressed, the hydraulic pressure formed in the hydraulic pressure chamber is exhausted such that the friction plate is separated from the power-varying unit.